Hydrogen-added (hydrogenated) block copolymers composed of a conjugated diene monomer and a vinyl aromatic monomer have, even without being vulcanized, elasticity comparable to vulcanized natural rubber and synthetic rubber at ordinary temperatures, have excellent weather resistance and heat resistance, and, moreover, have processability comparable to thermoplastic resins at high temperatures. Accordingly, such hydrogenated block copolymers are widely used for footwear, plastic modification, asphalt modification, viscous adhesives, home-use products, packaging materials of household electrical appliance and industrial components, toys, automobile parts, medical instruments, and the like.
Meanwhile, polypropylene-based resin compositions generally have excellent chemical resistance and mechanical properties, and are thus used in a broad range of fields such as packaging materials, miscellaneous articles, mechanical parts, automobile parts, and medical instruments. Moreover, polypropylene-based resin compositions are also used in the fields of sheet, film, tube, and the like, and for coating materials, connector materials, and the like of electric wires and cables for household electrical appliances, IT devices, etc. In these fields, there are demands for soft and transparent polypropylene-based resin compositions. With recent reduction in side of various devices, narrower electric wires and communication cables are used therefor and, accordingly, coating materials as well are becoming thinner. Consequently, there are also demands for polypropylene-based resin compositions having suitable flexibility and thin-wall molding processability from the viewpoint of shape retention.
In order to make polypropylene-based resin compositions soft and transparent, a method is used in which an elastomer such as an olefin elastomer is added to a polypropylene-based resin composition.
Moreover, for example, Patent Literature 1, in order to enhance the flowability and the transparency of a polypropylene-based resin composition, discloses a hydrogenated block copolymer having a specific melt flow rate value (MFR), comprising a specific amount of styrene, and having a specific amount of a hydrogenated polybutadiene block at a terminal, i.e., discloses a composition comprising a styrene elastomer and a polyolefin-based resin.
Furthermore, for example, Patent Literature 2, in order to impart high flowability and molding processability to a polyolefin-based resin composition, discloses a composition comprising a hydrogenated block copolymer obtained by hydrogenating a copolymer having a block composed of a vinyl aromatic monomer unit and a block in which the amount of vinyl bond of a conjugated diene monomer is 65 mol % or more and 85 mol % or less.